Secondary emission electron discharge device



Jan. 16, 1951 H. FINDLAY 2,538,560

SECONDARY EMISSION ELECTRON DISCHARGE. DEVICE Filed July 15; 1948 ZZ zz 14 Ul U 1U lz Z5 2f n 'e rg f llllll\\\\\\\\\\\/\l\ (li 2 i-L@ I IZ 15 v i u, si n 15 10 N /0 I ,A ma

I INVENTOR a w 4 m .I y. PWD/ HY 'YYQIMRMh-w. @-f m o 6o., a fw" ATTORNEY Patented Jan. 16, 1951 SECONDARY EMISSION ELo'rnoN DISCHARGE DEVICE l John Hamleyr'inciay; Upper-Montereale. J., as-

sgnor to .Westinghouse fElectricl Corporation, East Pittsburgh, Pai, agcorporationfof Penns'ybY Vania l Armi-cation rely 13, 194gtSer'iaiNaea4/25 6 Claims.; (Cl. 25M-17.4K

'Thisl'invention `relates to `a Asecondary 'emission electron discharge device,` andwhile the selected embodimentfor exemplifying the same in this disclosure is one utilizing a, beam of primary electrons Vfrom a cathode whichA are bunched in transit toward the opposing electrode, the invention; contemplates utilization in various discharge devices wherein secondary emission is employed forenh'ancementof Vthe Voutput therefrom'.

For purposes ofV explicit description, the present concept is related herein particularly in its application to la, Klystrontype'of electron discharge device chosen for purposes of illustrationV in the drawing. In the early stages of Klystron develop nient,` two resonators were ordinarily used with a drift space 'therebetween the electrons passing from a cathodethrough the first resonator where bunching influence was exerted Vso that bunching would progress through the drift space and be fullyY accomplished by the time the electronsreachedfthe second resonator. Energy of' the hunched electrons: passing through the second resonator to a collector' or anode therebeyond was extracted as output from' the second resonator.v Itlwas later: found, however; theta single resona-l tor4 could be utilized by substituting a reflector for` the collector so the electrons would pass through the resonator forwardly and be affected by the bunching influence thereof and after'passing throughthe resonator, be reflected to return in a.reverse direction, at which time energy from the bunchedelectrons was extracted byan out-- Zy secondary'emission-byuse of heat applied to 'the secondary f emitting electrode without 'introduce tion of counteracting primary emission therefr'om'."

Still further objectsv oi the invention will appear to those skilled.- in the f' art to which itappertains asthe-description progresses, both by direct=rec-` itation thereof and by implication from the cone` ytext. Y

Referring to the accompanying drawing" in i@ whichlike numerals ofV reference indicate similar 52 increase,:and showing increase of secondary ernia-v sion due to" temperature.

In', the specicembodiment of" the'invention` illustratedV in, saiddrawinggV both forms ofKly-V strons are shown in general configuration as 25v bodies of revolution about an axis, and each pro` put froml the single resonator This type of devicel f was known as a reex Klystron. The next forward 'step in they art comprised substitution of a secondary emitter in place of the reflector', and of course a ,proper use of potential relations and polaritlies for accomplishing desiredv electron flow. This device has been generally referred to as 'a secondary emission Klystron. The present inven- I l More specifically, van obiect of the invention-iis tfrobtainV greater output from a secondary etuissive Klystronor electron discharge devicero'f the beam type.V

f' Irrdetal, the invention proposes increase-fof [ill . I" ode 'to said electrode.

vides a coaxial resonator. il with a primary cath,.- ode l I on the axis opposite one end of the resonae tor and an opposed secondary emission electrode I2 also on said axis and opposite the other end of said resonator, the ends of theresonator'beingj perforate for passage of electrons thereinto from the cathode and frommthe said secondary emission electrode, yso that the structure'provides an axial passageway straight through from the cath.-

A more positivev polarity is applied to the secondary emission electrode than to the cathode, by Aa potential source f3, to cause primary electron flow4 from the cathode to tlsie' secondary electrode, and fa Vstill more positive' poi1 tefntiall is applied in iront of the 'secondary' electrede' by" potential 'source I4 to direct iiow' of secondary electrons back into the resonator. Iii Figure lthis more-positive potential 'is-applied to theresonatcr, whereas inA Figure v2. a grid l5' is providedbetween the secondary elecnodev andthe resonator for introducing this more positive poe tential'i By virtue Aof thefconstructionsrof either Figure I or Figure 2 and polarities provided there-'v for, pri-mary electrons are attracted to electrode l2 and produce agreater emission. of secondary electrons: therefrom which.V return, in hunched condition; to. the'rresonaton where'v Vthey give-,up energyfto an output loop l5 andcoaXiaLli-ne 11:1 providedi. for the-purpose: v More' in detaiirthe constructionshownfsituates the primary cathode emissive surface and the emissive surface of the secondary electrode transverse to the common axis on which they are located so as to be directly opposed and to constitute the ends of the passageway therebetween. The resonator has a portion` thereof intervening between the primary cathode and the secondary electrode and, with the openings in the ends of said resonator, constitutes part of said passageway from the cathode to the electrode, the openings through the ends of said resonator having perforate metal members across the same and designated herein as usual in the art, as grids. the cathode, these two grids for the two end walls of the resonator may be referred to as the near resonator grid I8 and the far resonator grid I9. Between the near grid I8 andthe cathode Accordingly, in the order of nearness to I I and also in said passageway, is a focusing grid 2li and between the focusing grid 2D and cathode II is a focusingr collar 2|, the interior region of which likewise constitutes part of said passageway.' VAn evacuated envelope 22v or enclosure, which includes the resonator in the present showing as part thereof, is provided for the cathode, secondary emission electrode, grids, and connecting passageway.

For fuller understanding of the invention it is desirable to explain brieily theories involved, with a vmathematical approach. Due to electron discharge from Icathode II to electrode I2 a cur-A range of a three to ten times increase, which can.,

be designated so that output efficiency of a secondary emitter Klystron will be times that.

of, a purely reflex device. Each is subject to the same operating and resonator constants k and sothat whereas the power output for a reex Klystron is the power output for a secondary emission,y

Klystron is P2=ka51 The desideratum of the present invention is to increase the value of to thereby increase output eiiiciency of the device.

I; The commonly employed silver-magnesium for secondary emitters gives an increase of secondary in the range of about three to five times overprimary electrons. It has been found that this multiplication range with silver-magnesium is approximately four 'to seven times secondary emission to primary emission, by an activated oxide secondary emitter, at ordinary anode operating temperature. `The secondary emitting -.electrode of the present invention preferably comprises a nickelor other suitable metal baseY member coated with an emission mixture, such as barium and strontium carbonate which, during exhaust, is broken down to barium and strontium 'oxide by venergizing the heater. The oxide 'coating is alsov activated in a manner Simi- 1'a`r to' the coating on a cathode. The secondary emission of such an electrode, as shown by thel curve in FigureA 3 is nearly constant. up to 400 C. which is a temperature above that encountered in secondary emitters of the prior art.

According to the present invention, I heat the secondary emitter during operation thereof, and it will be observed in Figure 3 that the curve has an upward slope between 500 to 850 C. and shows as acquiring a value of about at 850 C. Thus by raising the temperature of the secondary emitterto 850 C. the secondary emission becomes of the order of a hundred times the primary emission and thus accomplishes a very much greater output from the resonator than heretofore attainable. However, heating of the secondary emitter should not materially exceed the 850 C. temperature mentioned, since at about 900 C. the electrode would begin discharging primary electrons in objectionable quantity, primary emission therefrom being undesirable for the reason that the primary electrons therefrom would not be bunched whereas secondary electrons instigated by primaryy Yelectrons'from the cathode do have the desired bunching. A

Carrying out the concept outlined above, the construction herein shown provides a secondary emitting electrode I2 having substantially the structural arrangement ofthe primary cathode,A and in'more detail, comprises a hollow shell 23 supported at its rear by an insulator 24 and hollow at its forward portion to provide a chamber for aheater 25 therein. The forwardface of the shell disposed between the heater andthe resonator is the aforementioned base member coated with an activated emissive oxide orother mixture copiously emissive of secondary electrons and capable of being heated for obtaining an augmented supply of the secondary electrons..

Said member is made concave,.as shown, to .pro-fl vide focusing of the secondary electrons in a beam toward the opening cf the resonator. Appropriate lead-in wires for the heater andelec` trode are provided. The temperature -of the.

proportion of secondary emission of the second-,

ary emitter to primary emission from the primary emitter.

2. A secondary emission electron discharge. de. vice comprising a cathode emissive ofprimar-y.

electrons, means for directing saidelectronsY in a beam, a secondary emissive electrode opposite said4 cathode for receiving lprimary electrons therefrom, and a heater for ysaid electrode for increasing proportion of secondary electronsv from said secondary emitter to primary electrons-for the primary emitter.

3. A secondary emission electron discharge device-comprising a cathode emissive or primary electrons in one" direction, means for focusing said electronsin a beam in said direction, a sec ondary emissive electrode spaced from and op; posite'the 'cathode in the directionfof focusing of said beam, and a heater on vthe far side of fsaid4 electrode from the cathode for heatingrsaid elec-u tredeandjtherebyy increase secondary emission therefrom on impact of primary electrons of said beam on said electrode. v

4. A secondary emission electron discharge device comprising a primary emitter, a hollow electrode opposed to said emitter and having a surface emissive of secondary electrons, said surface being directed toward said primary emitter, and a heater within the hollow of said electrode for increasing proportion of secondary electrons from the electrode to primary electrons from said primary emitter. l

5. A secondary emission electron discharge device comprising a primary emitter, a secondary emitter having an electron emissive oxide coating thereon directed toward the said primary emitter and adapted to emit secondary electrons from impact of primary electrons thereon from the primary emitter, and means for heating said secondary emitter for increasing proportion of secondary electrons therefrom byimpact of primary electrons on said secondary emitter.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 2,411,601 Spencer Nov. 26, 1946 2,414,785 Harrison A Jan. 21, 1947 2,452,075 Smith Oct. 26, 1948 OTHER REFERENCES McAllister, Physical Review, vol. 21, 1923, p. 123` 

